Business Source Premier and Communication & Mass Media Complete are library databases containing full text articles on many advertising and marketing topics. Be flexible and creative with your search terms. Check the subjects listed in some of your best search results to get a sense of how articles on your topic are indexed in the database. Statista is another good source for company and brand information.
Because they are both hosted by Ebsco, you can search both of these databases at the same time - see the screenshots below to guide you through that search process.